XML 122 R106.htm IDEA: XBRL DOCUMENT
v3.25.3

SEGMENT INFORMATION - Narrative (Details) | 12 Months Ended
--- | ---
Sep. 30, 2025 employee segment | Sep. 30, 2024 | Sep. 30, 2023
Segment Reporting Information [Line Items] |  |  |
Number of operating segments | segment | 2 |  |
Employees represented by a union under a collective bargaining agreement (approximately) (%) | 20.00% |  |
Number of employees represented by a union under a collective bargaining agreement | employee | 1,105 |  |
Labor contract term | 5 years |  |
Accounts Receivable Benchmark | Customer Concentration Risk | Sonepar USA |  |  |
Segment Reporting Information [Line Items] |  |  |
Concentration risk, percentage | 13.00% | 17.00% |
Accounts Receivable Benchmark | Customer Concentration Risk | CED National |  |  |
Segment Reporting Information [Line Items] |  |  |
Concentration risk, percentage | 12.00% | 11.00% |
Sales Benchmark | Customer Concentration Risk | Sonepar USA |  |  |
Segment Reporting Information [Line Items] |  |  |
Concentration risk, percentage | 10.00% | 10.00% | 10.00%

X
- Definition Employees Covered By Collective-Bargaining Arrangement, Labor Contract Term + References No definition available. + Details
Name: | atkr_EmployeesCoveredByCollectiveBargainingArrangementLaborContractTerm
Namespace Prefix: | atkr_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Employees Covered By Collective-Bargaining Arrangement, Number + References No definition available. + Details
Name: | atkr_EmployeesCoveredByCollectiveBargainingArrangementNumber
Namespace Prefix: | atkr_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Employees Covered By Collective-Bargaining Arrangement, Percentage + References No definition available. + Details
Name: | atkr_EmployeesCoveredByCollectiveBargainingArrangementPercentage
Namespace Prefix: | atkr_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 280 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 42 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482810/280-10-50-42 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 275 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 18 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482861/275-10-50-18 Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 275 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 18 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482861/275-10-50-18 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 275 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 20 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482861/275-10-50-20 Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 275 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 18 -Subparagraph (d) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482861/275-10-50-18 Reference 6: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 275 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 18 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482861/275-10-50-18 Reference 7: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 275 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 18 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482861/275-10-50-18 + Details
Name: | us-gaap_ConcentrationRiskPercentage1
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 280 -SubTopic 10 -Name Accounting Standards Codification -Section 55 -Paragraph 49 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482785/280-10-55-49 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 280 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 18 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482810/280-10-50-18 + Details
Name: | us-gaap_NumberOfOperatingSegments
Namespace Prefix: | us-gaap_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_SegmentReportingInformationLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_ConcentrationRiskByBenchmarkAxis=atkr_AccountsReceivableBenchmarkMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ConcentrationRiskByTypeAxis=us-gaap_CustomerConcentrationRiskMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_MajorCustomersAxis=atkr_SoneparUSAMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_MajorCustomersAxis=atkr_CEDNationalMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ConcentrationRiskByBenchmarkAxis=us-gaap_RevenueFromContractWithCustomerProductAndServiceBenchmarkMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |